We asked a dozen national security experts what Congress should ask the top military commander in Iraq at this week's hearings. Here's what they came up with.

It's time for what's become a semiannual ritual: General David Petraeus comes to Capitol Hill. Last September, the top military commander in Iraq testified before several House and Senate committees in what was widely depicted as a make-or-break moment for the Bush administration and its war in Iraq. Wielding charts and graphs, Petraeus, who was accompanied by U.S. Ambassador to Iraq Ryan Crocker, claimed that the so-called surge of U.S. troops in Iraq was working and that "it is possible to achieve our objectives in Iraq over time." Such an outcome, he added, "will require a long-term effort." The questions he received from the legislators were mostly softballs. (Neither senators Hillary Clinton nor Barack Obama were impressive when questioning Petraeus.) But when Republican Senator John Warner asked Petraeus if the Iraq War "makes America safer," the general replied, "I don't know, actually. I have not sat down and sorted [it] out in my own mind." War critics zeroed in on that comment, yet Petraeus' performance was generally deemed a success, in that it appeared to have created political space (in the United States) for the war—six month's of space, at least. Petraeus told Congress that a decision on reducing the level of troops should be put off until March 2008 and that in half a year he would report back to Congress.

His return is scheduled for Tuesday and Wednesday, when he will testify before the armed services and foreign affairs committees of the Senate and the House. In recent weeks, the purported success of the surge strategy has been called into question, due to the rise of sectarian fighting with the Mahdi militia of Moqtada al-Sadr (an army also known as JAM) clashing with the Iraqi military. Before those battles occurred, Petraeus himself noted that the overall decline in violence (which in late 2007 dipped to 2005 levels) had not been accompanied by success on the political front: "No one feels that there has been sufficient progress by any means in the area of national reconciliation." And on Tuesday, senior Army and Marines Corps leaders told Congress that the surge of troops in Iraq has placed unsustainable stress on the U.S. military and rendered it less able to handle other conflicts. Yet Petraeus is not expected to provide Congress with testimony that will inconvenience the Bush administration or undermine its arguments for staying the course in Iraq. And there's no telling if members of Congress—including Democrats—will give Petraeus a more thorough grilling than he received in September, given that most members of Congress appear to have concluded that the House and the Senate cannot do much to slow or reverse Bush's war in Iraq.

So I asked various national security experts to provide questions that they would like to see posed to Petraeus. Here's what they want to know.

Andrew Bacevich, professor of history and international relations at Boston University:

—Many credit the "surge" with reducing the level of violence in Iraq. Yet violence continues and over the past several months has leveled out. How will you reduce violence to levels that are acceptable? What is the definition of "acceptable" in this context?

—You have written of counterinsurgency as an enterprise that typically takes 10 to 12 years to complete. Where do we stand today on that timeline? The war is now more than five years old. Are we halfway to accomplishing our mission? Or did the 10-to-12-year "clock" only begin when you took command and began to implement the army's revised counterinsurgency doctrine?

Larry Johnson, former CIA and State Department intelligence official:

—How many Iraqi army divisions are capable of conducting unilateral operations?

—Of those units, what is their ethnic (i.e. tribal) and sectarian composition? In other words, do we have mixed Sunni-Shiite units, or are we creating glorified tribal militias?

—Given that groups headed by people such as Abdul Aziz al-Hakim [leader of the Supreme Council for Islamic Revolution in Iraq] are very closely tied to Iran and considered allies of Prime Minister Nouri al-Maliki, what is the evidence that Iran is trying to destabilize a government filled by people who are sympathetic to Tehran?

Wayne White, head of the State Department's Iraq intelligence team 2003 to 2005 and an adviser to the Iraq Study Group:

—Regarding the JAM-related debacle in March, could the pitter-patter of relatively limited U.S. (and Iraqi government) attacks against some of Sadr's leaders and JAM cadres during a period in which so many of them were observing a ceasefire not only have had little impact on the JAM's overall capabilities, but also have constituted a provocation that increased the level of militancy (even a desire for revenge) among many of its fighters? Did this expand the JAM's popular base?

—With Hakim seemingly playing ball with Washington, Maliki doing likewise, and the Concerned Local Citizens [program] taking most Sunni Arab insurgents off the playing field, have many Shiites come to regard Sadr's organization as the only nationalist and anti-American force left standing? If so, what can—or should—be done about that?

Juan Cole, professor of history at University of Michigan:

—General Petraeus, you have done what you can do militarily. Its unclear that more can be done on that front, and yet there is still a fair amount of violence. The question is, what now? This is not facetious.

Sam Gardiner, retired Air Force colonel and expert on military strategy:

—Why did Iran help broker the cease-fire with the Mahdi Army?

A research professor at a military institute who asked not to be named:

—The Sunni Muslim Awakening groups now have between 80,000 and 100,000 members, according to press reports. These groups are slated to be reduced to 20,000 or 25,000 as the crisis in western Iraq becomes more manageable. What is the likelihood that these groups will accept a 75 percent demobilization even if noncombat jobs are found for them? Is it possible that they will see a pressing need to remain under arms to protect their home communities from a Shiite-dominated government? What would be the consequences if these groups remain in existence at the current level? If they are a short-term solution to the Al Qaeda in Iraq problem, might they also be a long-term building block for an Iraqi civil war?

—There is considerable fear that a residual Al Qaeda presence in western Iraq would lead to a terrorism campaign against neighboring countries. Yet when Al Qaeda mounted the November 2005 Jordanian hotel bombings, this led to a massive backlash and collapse of already limited Jordanian and Palestinian public sympathy for Al Qaeda, according to all relevant polling. Does this situation suggest that the danger of terrorism against other regional states is not as great as originally believed since it can lead to counterproductive results for Al Qaeda?

David Isenberg, military affairs analyst and adjunct scholar with the Cato Institute:

—What role do you see for both private military and security contractors in Iraq in the future?

—The surge was supposed to provide space for political reconciliation. What does the recent fighting in Basra and Baghdad and elsewhere in Iraq say about the supposed success of the surge?

—What are the likely average monthly costs for the Iraq war? Will they reach a predicted peak level of $12 billion a month?

—Would you advocate a long-term presence of U.S. troops in Iraq? If so, under which of the following scenarios? A combat scenario: approximately 55,000 military personnel in Iraq, operating at the same pace and conducting the same types of missions as the forces currently deployed there? Or a noncombat scenario: approximately 55,000 military personnel indefinitely stationed there in a manner similar to the current practice in Korea or Germany, with the troops rarely, if ever, engaged in combat operations?